cleaning horribly stained carpet?

Ok I picked up a LGCM a few weeks ago, and i love it, it works great but friday I had a van that looked like it had never been cleaned ever on the inside, stains all over the carpet, i spent about an hour on the right half of the carpet in the van and no matter how much i sprayed the meguiars APC solution from the LGCM on the carpet and scrubbed my ass off i couldnt get it out. Is this a case that its just so set in its impossible to get out or is there some badass miracle cleaner that would kick stains asses? I managed to get the carpet looking much brighter and cleaner but there were still some spots where you could clearly see stains stuck in the carpet.

Some stains are permanent and some need more than hand agitation/apc to clean them out. Pen ink, red kool aid, rust, hard water stains, blood, etc. are always going to give you problems if you're using the brush method. A heated extractor/steamer will make things easier but still won't guarantee perfect results, the motorized carpet scrubbers accelerate the process but I've even seen them fall short.

I think the key to removing carpet stains is as much about the right product as it is the right amount of product. If your APC is foaming while you scrub, theres probably more applied than necessary. Scrub away and reapply as needed, don't soak.

I remember a shop I worked at had maybe 60-75 cans of carpet dye on hand at all times. Nearly half were dk blue left over from the early 90s- that color must be stockpiled somewhere until the analog stereo dials come back into style.